software update keeps asking for the media

[Fulko Hew]

I'm trying to help someone (and I've seen it myself sometimes)...

On a newly installed system, it will probably come up and say
there are updates pending.  When you let it continue to
start the update process, it come up with a dialog box that
asks you for the installation media and allows you to either:
cancel, edit repo, continue.

I seems that sometimes, even if you've inserted the media
and press continue, it will still come back and ask for the
media again (without even checking for the media).

In the end... this guy can't update his system, because
it keeps asking for media, and keeps ignore the media.

And like I said, I've seen this too, but then sometimes,
and I don't know the condition, it does work, and then
it works for ever more.

Any comments, clues, or suggestions?